We keep all of our database scripts (data and schema/ddl) in version control. We also keep a central catalog of the changes. When a developer makes a change to a schema/DDL file or adds a script that changes the data in some way, those files are added to the catalog, along with the SVN commit number.
We have put together a small utility in-house that reads the catalog changes and builds a large update script based on the contents of the catalog by grabbing the contents from each revision in the catalog and applying them. The concept is pretty similar to the DBDeploy tool, which I believe originally came from Thoughtworks, so you may be able to utilize it. It will at least give you a good place to start, from which point you can customize a solution more directly suited to your needs.
Best of luck!
